1. Field of the Invention
The present invention relates to an electrophotographic photoreceptor. Particularly, the present invention relates to an electrophotographic photoreceptor having a high sensitivity and an excellent durability. Also, the present invention relates to an electrophotographic photoreceptor having an excellent durability, which causes less change in charge potential and residual potential even after being repeatedly used.
2. Discussion of Background Art
Heretofore, an inorganic photoconductive material such as selenium, zinc oxide, cadmium sulfide and silicon has been widely used as an electrophotographic photoreceptor. These inorganic materials have many merits and also have various demerits. For example, selenium requires hard production conditions and is easily crystallized by heat or a mechanical impact. Zinc oxide and cadmium sulfide have problems in moisture resistance and mechanical strength, and become poor in charging and exposing properties depending on a dye added as a sensitizer, and have a disadvantage in durability. Also, silicon requires hard production conditions and takes a high cost since a stimulative gas is used, and it is hard to handle it since it is sensitive to humidity. Further, selenium and cadmium sulfide have poisonous problems.
Recently, in order to overcome the disadvantages of these inorganic photosensitive materials, organic photosensitive materials using various organic compounds have been studied and widely used. Organic photosensitive materials include a monolayered photoreceptor having a charge generating agent and a charge transporting agent dispersed in a binder resin and a multilayered photoreceptor having a charge generating layer and a charge transporting layer separately provided to separately achieve functions. The photoreceptor referred to as xe2x80x9cfunction-separating typexe2x80x9d has such advantages that various materials can be widely selected so as to be suitable for each function and that a photoreceptor having an optional performance can be easily prepared, and accordingly many studies have been made.
As mentioned above, in order to satisfy requirements of a high durability and a basic performance demanded for an electrophotographic photoreceptor, development of novel materials and their combinations has been made and various improvements have been made, but satisfactory materials can not have been provided up to now.
As one of the above-mentioned examples, it is generally known that a kind of binder resins provide an influence on film properties and electrophotographic properties of an electrophotographic photoreceptor when an electrophotographic photoreceptor is produced by changing various binder resins to a specific charge transporting agent. For example, when an electrophotographic photoreceptor is produced by using polystyrene resin as a binder resin to a stilbene type charge transporting agent, electrophotographic properties including a drift mobility or a sensitivity are improved, but a film becomes weak or brittle and film properties are lowered. Also, when an electrophotographic photoreceptor is produced by using acrylic acid ester resin as a binder resin, film properties become satisfactory but electrophotographic properties are lowered.
However, although an organic material has many advantages which are not possessed by an inorganic material, but an organic material satisfying all of properties required for an electrophotographic photoreceptor has not been developed up to now. Thus, by repeatedly using, image qualities are deteriorated due to lowering of a charge potential, rising of a residual potential and a change in sensitivity. The causes of these deteriorations are not completely analyzed, but the deteriorations are considered to be caused by ozone generated by corona discharge at the time of charging, an active gas such as NOX, light exposure, ultraviolet rays included in destaticizing light or heat which causes decomposition of a charge transporting agent. In order to prevent the deteriorations, JP-A-1-44946 proposes to combine a hydrazone compound and an antioxidant, and JP-A-1-118845 proposes to combine a butadiene compound and an antioxidant, but a product having a satisfactory initial sensitivity is not sufficiently improved in respect of preventing the deterioration caused by repeated use and a product having less deterioration due to repeated use is poor in respect of initial sensitivity and charging properties. Thus, these conventional techniques have not achieved satisfactory effects up to now.
Accordingly, an object of the present invention is to provide an electrophotographic photoreceptor having a high sensitivity and a low residual potential in the initial stage, which is stable to ozone, light, heat and the like and is not deteriorated by fatigue even by repeatedly using.
Also, the present inventors have intensively studied an electrophotographic photoreceptor excellent in sensitivity and durability, and have discovered that an electrophotographic photoreceptor containing an indane compound and a polycarbonate resin provides excellent sensitivity and durability. Thus, an object of the present invention is to provide an electrophotographic photoreceptor having improved electrophotographic properties including sensitivity and residual potential and also having an excellent durability by combining an indane compound and a polycarbonate resin.
The present invention resides in an electrophotographic photoreceptor having at least one indane compound of the following formula (1) and at least one polycarbonate resin of the following formula (4) in a weight ratio of from 2:8 to 7:3 on an electroconductive support;
said at least one indane compound being expressed by the formula (1), 
(wherein Ar1 is a substituted or unsubstituted aryl group, Ar2 is a substituted or unsubstituted phenylene group, a substituted or unsubstituted naphthylene group, a substituted or unsubstituted biphenylene group or a substituted or unsubstituted anthrylene group, W is a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, X is a substituted or unsubstituted aryl group, a monovalent group of the formula (2), 
or a monovalent group of the formula (3), 
(wherein R1 is a hydrogen atom, a lower alkyl group or a lower alkoxy group, R2 is a hydrogen atom, a halogen atom or a lower alkyl group, Y is a hydrogen atom or a substituted or unsubstituted aryl group, and m and n are an integer of from 0 to 4)), and
said at least one polycarbonate resin being expressed by the formula (4), 
(wherein R3 and R4 are respectively independently a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, R3 and R4 together may form a ring, R5, R6, R7, R8, R9, R10, R11 and R12 are respectively independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group or a halogen atom, p is a positive integer, q is 0 or a positive integer, p and q satisfy the formula 0xe2x89xa6q/pxe2x89xa62, Z is a substituted or unsubstituted C1-C5 alkylene group, a substituted or unsubstituted 4,4xe2x80x2-biphenylene group or a divalent group of the formula (5), 
(wherein R13 and R14 are respectively independently a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, R13 and R14 together may form a ring, R15, R16, R17 and R18 are respectively independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group or a halogen atom, and r is 0 or an integer of from 1 to 3)).
However, when only one kind of polycarbonate resin is used in the above electrophotographic photoreceptor, the polycarbonate resin of the formula (4) does not have a structure wherein R3 and R4 are a methyl group, R5, R6, R7, R8, R9, R10, R11 and R12 are a hydrogen atom, and q is 0.
By using the electrophotographic photoreceptor of the present invention, electrophotographic properties such as sensitivity and residual potential can be improved and a high durability can be achieved.
Examples of a charge transporting agent of an indane compound expressed by the above formulae (1) to (3) are illustrated below. 
Examples of a polycarbonate resin expressed by the above formulae (4) to (5) are illustrated below, but the polycarbonate resin used in the present invention should not be limited thereto. 
The electrophotographic photoreceptor of the present invention has a photosensitive layer containing said at least one indane compound and said at lest one polycarbonate resin.
Also, the present invention resides in an electrophotographic photoreceptor having a photosensitive layer containing at least one indane compound of the following formula (1) and an organic additive containing at least one atom selected from the group consisting of nitrogen, oxygen, phosphorus and sulfur for an electrophotographic photoreceptor on an electroconductive support;
said at least one indane compound being expressed by the formula (1), 
(wherein Ar1 is a substituted or unsubstituted aryl group, Ar2 is a substituted or unsubstituted phenylene group, a substituted or unsubstituted naphthylene group, a substituted or unsubstituted biphenylene group or a substituted or unsubstituted anthrylene group, W is a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, X is a substituted or unsubstituted aryl group, a monovalent group of the formula (2), 
or a monovalent group of the formula (3), 
(wherein R1 is a hydrogen atom, a lower alkyl group or a lower alkoxy group, R2 is a hydrogen atom, a halogen atom or a lower alkyl group, Y is a hydrogen atom or a substituted or unsubstituted aryl group, and m and n are an integer of from 0 to 4)).
By having the above photosensitive layer, the electrophotographic photoreceptor of the present invention provides stable electrophotographic properties including satisfactory charge potential and residual potential and also provides a high durability.
Further, the present invention resides in an electrophotographic photoreceptor, wherein the above organic additive containing at least one atom selected from the group consisting of nitrogen, oxygen, phosphorus and sulfur for an electrophotographic photoreceptor is contained in an amount of from 0.05 to 30 wt % to the indane compound of the formulae (1) to (3);
the organic additive being at least one compound selected from the group consisting of an organic phosphite compound of the formula (6), 
(wherein R19, R20 and R21 may be the same or different, and are a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, an allyl group or a substituted or unsubstituted aryl group, provided that R19, R20 and R21 are not hydrogen atoms at the same time),
a triphenylated phosphorus compound of the formula (7), 
(wherein R22, R23, R24, R25, R26 and R27 may be the same or different, and are a hydrogen atom, a halogen atom, a hydroxyl group, an amino group or an alkyl group),
a thioether compound of the formula (8),
R28xe2x80x94Sxe2x80x94R29xe2x80x83xe2x80x83(8) 
wherein R28 and R29 may be the same or different, and are a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, an allyl group or a substituted or unsubstituted aryl group),
a hydroquinone compound of the formula (9), 
(wherein R30, R31, R32 and R33 may be the same or different, and are a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, an allyl group or a substituted or unsubstituted aryl group),
a benzotriazole compound of the formula (10), 
(wherein R34 and R35 may be the same or different, and are a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, an allyl group or a substituted or unsubstituted aryl group),
a benzotriazole-alkylenebisphenol compound of the formula (11), 
(wherein T is a hydrogen atom, a halogen atom, an alkyl group, a cycloalkyl group, an alkoxy group or an aralkyl group, R36 is an alkyl group, a cycloalkyl group, an aryl group, an alkoxy group or an aralkyl group, R37 is a hydrogen atom, an alkyl group or an aryl group, R38 and R39 may be the same or different and are an alkyl group, a cycloalkyl group, an aryl group or an aralkyl group),
a hydroxybenzophenone compound of the formula (12), 
(wherein R40 and R41 may be the same or different, and are a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, an allyl group or a substituted or unsubstituted aryl group),
hindered phenol compounds of the formulae (13) and (14), 
(wherein R42 is a lower alkyl group, R43, R44, R45 and R46 may be the same or different, and are a hydrogen atom, a substituted or unsubstituted lower alkyl group or a substituted or unsubstituted lower alkoxy group), 
(wherein R47 is a lower alkyl group, R48, R49 and R50 may be the same or different, and are a hydrogen atom, a substituted or unsubstituted lower alkyl group or a substituted or unsubstituted lower alkoxy group, q is an integer of from 2 to 4, E is an oxygen atom or an aliphatic divalent group when q=2 and is an aliphatic trivalent group or an aromatic trivalent group when q=3, and an aliphatic tetravalent group when q=4),
a hindered amine compound of the formula (15), 
(wherein R51, R52, R53 and R54 may be the same or different, and are a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, Z is a group of atoms necessary for forming a nitrogen-containing heterocyclic ring, and one of a pair of R51 and R52 and a pair of R53 and R54 may form a double bond within Z, and u and j are organic residues), and
a salicylate compound of the formula (16), 
(wherein R55 and R56 may be the same or different, and are a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, an allyl group or a substituted or unsubstituted aryl group).
The electrophotographic photoreceptor of the present invention has a photosensitive layer containing at least one indane compound and at least one organic additive (hereinafter referred to as xe2x80x9cadditivexe2x80x9d) containing at least one atom selected from the group consisting of nitrogen, oxygen, phosphorus and sulfur.
Examples of a charge transporting agent of an indane compound expressed by the formulae (1) to (3) are illustrated above.